The present invention relates to an auxiliary battery life determining device that determines the life of an auxiliary battery for use in case of emergency.
An emergency reporting system or the like may sometimes be loaded with an auxiliary battery, in addition to a main battery (a lead-acid battery) for normal operation, so as to exclude the possibility of the system becoming inoperative in emergencies.
However, the auxiliary battery for emergency use is also exhausted by spontaneous discharge, and hence in some cases it cannot be used even if switched from the main battery in an emergency.
Incidentally, there have been proposed devices for detecting or indicating the amount of power remaining in a secondary battery; for example, Pat. Pub. Gazette No. 10-153647 adopts a scheme that compares the output voltages from the secondary battery under no-load conditions and under load conditions, and uses the difference to detect the remaining battery power, but no proposal has been made of a device of the type that refers to discharge curves different according to the depth of discharge and detects and indicates the remaining battery power.
With the conventional battery life determining devices described above, since the difference between the output voltages under no-load and load conditions with different depths of discharge cannot accurately be detected due to different discharge characteristics, the lifetime of the auxiliary battery cannot be detectedxe2x80x94this makes it impossible to avoid the possibility that the auxiliary battery cannot be used in case of emergency.
The present invention is intended to solve the above-mentioned problem, and has for its object to provide an auxiliary battery life determining device that permits accurate detection of the service life of the auxiliary battery.
An auxiliary battery life determining device according to a first aspect of the present invention is adapted to measure the terminal voltage and temperature of an auxiliary battery, calculate the depth of discharge of the auxiliary battery from the measured results and determine the useful life of the auxiliary battery.
This allows detection of the auxiliary battery life, making it possible to preclude the possibility that the auxiliary battery cannot be used in case of emergency.
According to another aspect of the present invention, the auxiliary battery determining device is adapted to indicate that the auxiliary battery needs replacing when the depth of discharge of the auxiliary battery exceeds a reference depth of discharge.
This ensures replacement of the auxiliary battery before the auxiliary battery cannot be used.
According to another aspect of the present invention, the auxiliary battery life determining device is adapted to refer to discharge curves of different depths of discharge, calculate the amount of power remaining in the auxiliary battery from the measured results by the measuring means and indicate the calculated remaining power of the auxiliary battery.
This permits accurate detection of the life of the auxiliary battery.
According to another aspect of the present invention, the auxiliary battery life determining device is adapted to refer to discharge curves of different depths of discharge, calculate the useful time of the auxiliary battery from the measured results by the measuring means and indicate the calculated useful time of the auxiliary battery.
This permits accurate detection of the timing for replacement of the auxiliary battery.
According to another aspect of the present invention, the auxiliary battery life determining device is adapted to periodically cause a discharge of a constant current until the number of times the constant current is discharged reached a predetermined number of times.
This permits detection of the self discharge ratio of the auxiliary battery and the number of times the constant current is discharged therefrom, enabling its useful time to be calculated by a microcomputer or the like and hence the lifetime of the auxiliary battery to be detected.
According to another aspect of the present invention, the auxiliary battery life determining device is adapted to measure the discharge current terminal voltage and temperature of the auxiliary battery when connected to a dummy load, calculate the depth of discharge of the auxiliary battery from the measured results and decide the lifetime of the auxiliary battery based on the calculated depth of discharge.
This allows detection of the auxiliary battery life, making it possible to preclude the possibility that the auxiliary battery cannot be used in case of emergency.
According to another aspect of the present invention, the auxiliary battery life determining device is adapted to indicate that the auxiliary battery needs replacing when the depth of discharge of the auxiliary battery when connected to a real load exceeds a reference depth of discharge.
This ensures replacement of the auxiliary battery before the auxiliary battery cannot be used.
According to another aspect of the present invention, the auxiliary battery life determining device is adapted to refer to discharge curves of different depths of discharge, calculate the amount of power remaining in the auxiliary battery connected to the real load from the measured results by the measuring means and indicate the calculated remaining power of the auxiliary battery.
This permits accurate detection of the life of the auxiliary battery.
According to another aspect of the present invention, the auxiliary battery life determining device is adapted to refer to discharge curves of different depths of discharge, calculate the useful time of the auxiliary battery connected to the real load from the measured results by the measuring means and indicate the calculated useful time of the auxiliary battery.
This permits accurate detection of the timing for replacement of the auxiliary battery.